Recent work has characterized aspects of visual short-term memory (VSTM) in infancy, uncovering dramatic, rapid developmental change in the first postnatal year. In real-world cognitive tasks, however, VSTM is not used in isolation-it is used to plan eye-movements, information that is attended is encoded in VSTM, and information stored in VSTM is compared with currently available information. Although such interactions are well established in adults, at present we know little about such interactions in infancy. Moreover, there is an increasing realization in the field of cognitive development that solely understanding the development of abilities in isolation does not provide a complete understanding of how such abilities develop. As skills and abilities develop, they likely create opportunities to practice, scaffold, and creating opportunities to use other emerging skills, both enhancing infants' use of the emerging skill and promoting additional development of that skill. Therefore, an important step in our understanding of the early development of VSTM is to examine how VSTM is used and co-develops with other cognitive skills and abilities. The relation between attention and VSTM is particularly important for several reasons. First, powerful and bi-directional relations between VSTM and attention have been uncovered in adults. In adults, information that is attended is encoded in VSTM, and information encoded in VSTM can direct attention in visual search, planning eye-movements, and making comparisons between remembered and now visible scenes. Second, VSTM undergoes rapid and dramatic developmental change between 6 and 8 months, precisely when other work has shown large changes in attentional control. Thus, the two cognitive skills develop along similar timescales. Third, attention and VSTM are subserved by the same underlying brain regions. Thus, as these regions develop, we would expect developmental changes in both these abilities. Finally, attentional strategies may help infants overcome the overwhelming amount of information that they encounter in each moment, facilitating their use of VSTM in cluttered visual scenes. Work with adults has shown that individual differences in attentional strategies are related to individual differences in VSTM capacity. And, work with infants suggests that they can use a salient cue to help focus attention on only one item in a scene. The proposed work will build on the rich foundation of previous work examining VSTM and attention in isolation. The focus will be on the transition between 6 and 10 months, a time when both VSTM and attentional processes undergo rapid and significant change. To examine how the contents of VSTM control attention, this project will use eye-tracking methods to investigate the role of VSTM in eye-movements and visual search (Experiments 1 and 2). To examine how attentional cueing contributes to VSTM encoding, this project will use both preferential looking and eye-tracking methods to examine infants' change detection in cluttered visual scenes-in this case, arrays of multiple items (Experiments 3 and 4). Finally, to examine the co-development of these abilities, this project will assess longitudinally VSTM and attentional abilities (Experiment 5). Together, these experiments will add considerably to our understanding of the typical development of this critical cognitive ability. PUBLIC HEALTH RELEVANCE: Storing information in visual short-term memory (VSTM) is crucial for many cognitive tasks including making and correcting eye-movements, searching a visual scene for an important target, and comparing two visual images that cannot be simultaneously foveated. Without VSTM it would be impossible to determine that the view of the world is the same before and after an eyeblink, that an eye-movement had landed on the intended target, or that the object that appears from one side of a couch is the same as the object that disappeared behind the couch a moment before. This ability therefore is essential for much of cognitive development and without it infants would have difficulty learning about the objects, people, and events they encounter. VSTM depends on parietal cortical regions. This is a vulnerable region that has been found to be compromised in development disorders such as Autism Spectrum Disorder (ASD), Williams Syndrome (WS), and Fragile X syndrome (FXS). Little is known about VSTM in such populations, but we may predict that such individuals also would have deficits in VSTM. Indeed, substantial deficits in VSTM have been revealed in schizophrenia, a neurodevelopmental disorder that unfolds over a much longer time scale. Understanding the typical development of VSTM in infancy, therefore, may provide another avenue for identifying children who are at the beginning of atypical developmental trajectories. The knowledge gained from this project, therefore, will provide key understanding to a fundamental cognitive ability central to many aspects of typical development, and may provide an avenue for future identification of children at risk for atypical development. Therefore, this project will add to our ability to insure the healthy development of all children.